basically as soon as the game starts I send my probe in and hide in shadows.

I build forge and gateway, and keep pumping out probes. then when I have two Z. I go harass. In the same instance I build cannons and slowly work them towards their minerals. I find it's best to get your first plyon out still hidden, and then the first cannon out right next to it, still in shadows. That way when it's completed, and only then, build them as close as you can to their miners. So when they go try to stop the build when they appear on their mini-map, they get shot by the first cannon. Otherwise it's easy for them to stop it. Then they have to pull off miners to attack the cannons being built, because their troops should be trying to deal with the waves of Zs. This way they need to deal with both your Zs, that you keep pumping out, and the cannons threatening the miners.

Works out fairly well, even when some put up a fight I just stop building cannons and start producing more ground troops. I kill their economy so even if they stop the advance, I'll have the next wave to destroy. Only had a few people stop it, and even then I would win due to my overwhelming amount of troops.

you leave your base pretty open, so build one or two cannons inside the base, or keep some Zs to guard, or build cannons at their entrance as well.